This invention relates generally to roller bearing cages and, more particularly, to roller bearing cages of "sigma" configuration.
Roller bearings commonly employ separators, retainers or cages to maintain separation and alignment of the rollers. Although the terms are frequently used interchangeably, the term "cage" is often used to describe a device that retains the rollers both radially and axially. Thus, a roller bearing cage prevents rollers from moving axially or radially out of the cage, allowing the cage and rollers to be handled as a bearing subassembly.
One particular type of roller bearing cage is known as a sigma cage. As illustrated in FIG. 1, a typical sigma cage 10 has annular end rims 12 and 14 joined together by crossbars 16 to form slots 18 for receiving rollers, not shown. Crossbars 16 have a central portion 20 offset radially inwardly from laterally outward portion 22 and 24 such that, when viewed in cross-section, end rims 12 and 14 and crossbars 16 resemble the Greek letter "sigma."
End rims 12 and 14 extend axially toward each other with cylindrical portions 26 and 28, respectively. Cylindrical portions 26 and 28 provide end surfaces of slots 18 such that axial movement of the rollers is restricted. Edge surfaces on central portion 20 prevent radially inward movement of the rollers and edge surfaces of laterally outward portions 22 and 24 prevent radially outward movement of the rollers.
The maximum load carrying capacity of such sigma cages is limited by the restricted roller length. The crossbars have limited elasticity and cause distress to the rollers during insertion into the cage. Also, lubrication flow is restricted by the continuous radially oriented surfaces of the end rims. And, fatigue strength is reduced by the corners of the slots and the tight end rim corner radius, which increase the stress concentration factor.
Manufacture of such sigma cages usually requires a rolling mill and high cost scissor blank cutoff tooling. Welding of the end rims requires a subsequent flange surface grind operation. Also, piercing of the slots creates burrs that must be removed by grinding, tumbling or other metal finishing operations to provide conformity to a pilot raceway surface. And, a special multislide wrap mechanism, blank rotator, or post pierced stock twister may be required.
The foregoing illustrates limitations known to exist in present roller bearing cages of sigma configuration. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one of more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.